Ideas to Improve Driven Pile Foundation Design and Installation Procedures-Paper

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The paper examines why driven pipe piles may achieve less axial capacity than predicted, particularly in plastic cohesive soils and for large-diameter, open-ended piles. It presents a SHANSEP-based method for estimating pile side adhesion from soil overconsolidation ratio, adjusted by an empirical construction influence factor (CI) to account for installation effects.<br /><br />Pile setup—the increase in resistance as excess pore pressure dissipates—can substantially raise capacity over time. In one example, piles reached about 60% of their long-term side resistance after seven days and 87% after 28 days. Design load tests should therefore allow adequate setup time, often 28–56 days in thick cohesive deposits, and acceptance criteria should reflect setup.<br /><br />Several installation practices can reduce side resistance: re-driving after setup, vibratory installation in cohesive soils, slow jacking, long interruptions during installation, and repeated shearing of the soil–pile interface. Case histories show that vibratory driving may reduce resistance by roughly 40–50%; re-driving and prolonged installation can also cause significant losses. The paper proposes preliminary CI values to help estimate these effects, but stresses that they are based on limited case histories and are not universally applicable.<br /><br />The authors recommend planning installation methods early, accounting for construction impacts in design, and using project-specific instrumented pile tests to measure setup and capacity. Where setup is important, paired indicator piles can help distinguish capacity gains from setup from losses caused by repeated restrikes. Recognizing and testing installation effects can improve pile design, acceptance criteria, and construction planning.

Keywords

driven pipe piles

axial capacity

plastic cohesive soils

large-diameter piles

open-ended piles

pile setup

side resistance

installation effects

vibratory driving

SHANSEP method